Reposted from kbman by kbman
Editor's Note: Another quick update. I remembered the aid links this time :) -- kbman
There have been a number of developments I want to mention. Again I need to make this a quick rundown as I need to work on projects I've been neglecting.
Units 2 and 3 are no longer able to hold steam pressure. Their water level has risen a few inches and the last reported temperatures were 143 C and 121 C at the lower Reactor Pressure Vessel head. It would be expected that their pressure would be comparable to the roughly 4 or 5 times atmospheric pressure in the unit 1 reactor vessel system. Instead they are showing near atmospheric pressure.
What this all means is that somewhere above the water line, something is letting enough air/steam out of the system to keep pressure from being able to rise. The most likely causes would be leaks in any of a number of relief valves and shutoff valves. And yes, a crack could also provide the same pressure relief, but given the sequence of events and the corrosive chemistry of the seawater, leaky seals and valves were to be expected after a time, cracking of the vessel was not. When you see symptoms consistent with expected causes it makes little sense to blame it on very different and far more unlikely causes. I don't discount the possibility that an unforeseen combination of effects has caused a split in the pressure vessel. To date I have not read anything from folks knowledgeable in metallurgy or materials testing comment on this to provide an explanation of how it could happen and how conditions during this emergency could have caused it.
It's a much simpler mechanism for one or more pressure relief valves to have become unable to close after cycling several times to vent steam. There are corrosive impurities building up everywhere inside which can affect these valve sealing surfaces far more quickly than they can the thick stainless steel Reactor Pressure Vessel walls.
There are experts in various specialties arriving in Japan from France and the USA to assist in managing the effort to achieve greater stability at the site. They have discussed such items at bringing in tanker ships to store water for decontamination processing. There were also reports of "wrapping the reactors" in some type of fabric to reduce radioactive releases. From what I could gather they were talking about tenting the reactor buildings with some filtering fabric to limit the ability of particulates to leave the site. The only link I saw was in Japanese ... so it goes.
The process of pumping down the turbine buildings continues slowly as they keep finding places to move less contaminated water to open up local storage. The water in the trench at unit 1 is far less radioactive than that at unit 2. They do not have measurements at unit 3 due to debris - no explanation is given in the summary as to how the debris is hampering this effort. We do know that the water in the unit 3 turbine building is radiologically hot because that was where the workers received the radiation burns on their feet. Given that the turbine building drains into the trench, it is likely that the trench at unit 3 is more like that at unit 2 than at unit 1.
Draining the turbine buildings is critical for work to be able to proceed getting the pumps properly tested, re-primed, and ready to flow. They also need to test and confirm the ability of the heat exchangers to perform their function. This means having large pumps operating which bring in seawater to provide cooling. Until those pumps can operate they can't use the heat exchangers because there would be no place for the heat to go.
We haven't heard much about fuel pools the past few days. The temperature in pool 2 was recently measured at 46 C. Not where they want it but not bad. No measurements available for 1,3 and 4. At units 5 and 6 and the common pool temperatures are above normal but not alarmingly so.
Also, reports that the chairman had committed suicide were yet another rumor, somewhat sick I might add. From Kyodo News:
Tsunehisa Katsumata, the company's chairman, said at a news conference nearly three weeks after a powerful earthquake and tsunami prompted the crisis that ''several weeks will be too short'' to stabilize overheating reactors and spent-fuel pools.
As to the managerial responsibilities he and President Masataka Shimizu should bear, Katsumata said, ''Our greatest responsibility is to do everything to bring the current situation to an end and under control.''
Shimizu was hospitalized Tuesday for hypertension and dizziness, TEPCO said earlier Wednesday. But the chairman said, ''We have not been aware of any intention of our president to resign.''
Katsumata, who has already taken over Shimizu's role temporarily in leading efforts to bring the crisis under control, said that it will not take long for the ailing president to return to work and resume handling the crisis.
From this I gather that the kernel of truth to the rumor was that something was wrong with the company president.
As mentioned above, I have a busy afternoon ahead. I'll do what I can to answer any questions as soon as I get a chance, no later than early evening.
Also, please remember there is much suffering going on in Japan as a result of all of the things that have been thrown at them the past few weeks. If you can afford to do so, please send something their way. Here are two ways to do that
The Japanese Red Cross Society and Shelter Box USA
Also, here is a link for some great video of the plants that b00g13p0p brought to my attention. And to get a sense of the size of some of these components, here is a link I found last night with various BWR pictures and diagrams.